1. Does an aeronautical study need to be done if my structure is below 499’?

Each case is different. Completion of another Aeronautical Study will be determined in accordance with the requirements of 14 CFR Part 77. The FAA OE/AAA website (https://oeaaa.faa.gov) has a notice criteria tool which can help determine if filing is a requirement. The link for the notice criteria tool is located on the left side of the page.

2. If a client is upgrading the lighting system on their existing tower, the lights utilized need to conform to which AC?

If a client has an existing tower, with determination prior to December 4, 2015, that meets previous marking and lighting “K” criteria, they are not required to change marking and lighting. However, if they wish to change marking or lighting from what was specified in the initial determination, they should submit for a Marking and Lighting study on our website (https://oeaaa.faa.gov), requesting the change by submitting Form 7460-1. When filing, they should include the proposed change and note that it is consistent with AC 70/7460-1L CHG 1 and AC150/5345-43H, Specification for Obstruction Lighting Equipment

3. Can an owner change lighting to be in compliance with the current version of the AC?

Yes. However, a request for marking and lighting study should be submitted electronically on our website (https://www.oeaaa.faa.gov) utilizing the electronic 7460-1 form. Indicate the marking and lighting change that is desired, and that it is in compliance with the new AC. The FAA will conduct a marking and lighting study for the existing structure and issue a new determination specifying marking and lighting in accordance with the new AC.

4. Why do I need to request a marking and lighting change?

To remain in compliance with Title 14 CFR Part 77 and enable the FAA to ensure the change is captured in the Digital Obstacle File and made available to the flying community.

5. If a new configuration of lighting system to be utilized on an existing structure is already lit, does the owner have to refile a 7460-1?

Yes. They should submit for a Marking and Lighting study on our website (https://oeaaa.faa.gov), requesting the change by submitting Form 7460-1.

6. Why was the AC changed to require all red lights and paint for all wind turbines in a farm regardless of spacing for anything above 499 feet AGL?

The height of turbines has increased significantly which requires larger rotors and greater distance between each structure. FAA has determined it is in the best interest of safety to require red lights and paint for each turbine over 499 feet AGL.

7. Why is the lighting requirement for L-810 changed from solid to blinking for structures between 151’ – 350’?

This change was enacted to save the lives of small migratory birds that were attracted to the solid lighting and using it as a point for navigation. The birds would exhaust themselves circling a solid obstruction light or running into the structure itself. The FAA worked closely with wildlife biologist to determine the best lighting intensity for a pilot’s awareness and be less attractive to birds.

8. The AC states that “structures determined prior to December 4, 2015, would be required to be marked and lighted in accordance with AC 70/7460-1K.” If the structure was studied under an AC prior to 1K, should it be marked and lighted in accordance with the AC under which it was studied, as opposed to 1K? Moreover, while the FAA noted that existing towers would be grandfathered under prior ACs, the FAA’s recent News Update instructs that “new tower lighting schemes should now follow the revised guidance, and operators of towers with the old lighting system should submit plans explaining how and when they will transition to the new standards.” Please elaborate on this statement.

The word “Determination” was used in the wrong context when referenced in the News Update. A more accurate statement would read:
Based on the results of that research, the FAA updated its Advisory Circular (AC) for obstruction marking and lighting in December 2015. New tower lighting schemes determined on or after December 4, 2015 should follow the revised guidance. While operators of towers determined prior to December 4, 2015 are grandfathered under the previous Advisory Circular, if they elect to update their lighting scheme, they should submit plans explaining how and when they will transition to the new standards.

9. Does the FAA expect existing towers with L-810 lighting (150’ – 350’) to convert the L-810s to flashing?

No, the FAA expects towers to be marked and lighted in accordance with the version of the AC in existence at the time of the associated determination. Structures determined prior to December 4, 2015, would be required to be marked and lighted in accordance with AC 70/7460-1K, as a condition of the determination of no hazard. Likewise, structures determined on or after December 4, 2015 have been issued determinations that specify marking and lighting in accordance with AC 70/7460-1L CHG 1.

10. The AC states that “Flashing L-810 lighting has a delayed effective date and becomes mandatory on September 15, 2016.” What does this statement imply?

The recommendation for flashing L-810 lighting is the result of avian studies and designed to reduce the instances of bird deaths associated with steady burning lights. The report can be found at http://www.airporttech.tc.faa.gov/Download/Airport-Safety-Papers-Publications. The delay in expectations that new towers will be equipped is to ensure industry has time to design, test and certify, and manufacture the equipment. Because of other significant changes to the AC, the FAA decided to not delay publication to align with availability.

11. If owners must refile all changes, what is the expected turnaround time to receive a new determination? Since owners were encouraged to get started, should owners implement the changes, then file; or should owners wait? If an owner files to make a change, will the new determination not be issued until Sept. 15, 2016, or must that owner wait until then to file?

Owners are encouraged to file as early as feasible. The minimum requirement is 45 days, and the FAA seeks to make all determinations within that time frame.

12. If requesting flashing L-810s, will the new determination not be issued until Sept. 15, 2016, or must that owner wait until then to file?

The owner may file immediately. The determination will be issued by the FAA as soon as possible, and seeks to make determinations within 45 days of receipt.

13. What does the word “encourage” in the FCC’s statement issued regarding the AC: “With the implementation of AC 70/7460-1L CHG 1, the Bureau encourages owners of existing registered antenna structures to eliminate the use of L-810 steady-burning side lights as soon as possible.”

The FCC is hopeful that the change to flashing L-810s will reduce the number of avian deaths, and therefore encourages owners to eliminate the steady-burning side lights. This is not a mandatory change as noted above. In the event they choose to modify the lighting, they must notify the FAA for a marking and lighting change.

14. If an owner plans to simply turn a side light off or make it flash instead of burn steady, in accordance with the AC, does that require a new filing?

Yes, if the owner wishes to change the marking and lighting from what was initially contained in the associated determination of no hazard, the owner must notify the FAA via the electronic 7460-1 on the website (https://oeaaa.faa.gov). This will allow the FAA to validate the marking and lighting request meets conspicuity requirements, issue the associated determination, and capture the change in the digital obstacle file.

15. Chapter 7 now allows medium dual lighting for structures up to 700’ in height. Previously, it was only allowed on structures up to 500’. Do we need to file a new 7460-1 to request this change in lighting for the towers between 500’ – 700’? Will the FAA restudy the tower? What happens if the study now shows that the tower height is impermissible?

Yes. A request for marking and lighting study should be submitted electronically on our website (https://www.oeaaa.faa.gov) utilizing the electronic 7460-1 form to request a change for towers between 500’ and 700’. Indicate the marking and lighting change that is desired, and that it is in compliance with the new AC. The FAA will conduct a marking and lighting study for the existing structure and issue a new determination specifying marking and lighting in accordance with the new AC. Marking and Lighting studies will not result in a determination of hazard based on the height, but will specify what marking and lighting requirements are associated with the determination of no hazard. If the request includes a change in location or height, it may result in a determination of hazard, as a new study.

16. What caused your team to decide to take a deeper dive into the impact of medium dual lighting? Was there a specific event, or series of events that led to the need for problem solving?

The research that was recently conducted on refining the limits of medium and high intensity lighting was in response to an effort to maintain consistency, and enhance the safety of towers. There was not a specific event or series of events that prompted this research. The reasons for the changes can be divided into four major reasons:

A and B

A. As of version AC 70/7460-1K, the FAA Style D (Medium White for day and night) and Style E (Medium Intensity Dual) each provide for either 2,000cd white or red lights to be used on towers up to 500 feet AGL at night. In the same version of the AC, FAA Style A (All red lighting for day and night) allows for the same 2,000cd red lights to be used on towers up to 700 feet AGL at night. This creates a non-standard situation in which you could have two towers that are lit differently because of what lighting style the proponent elected to use. The changes that were made in version 1L basically allow Style D and Style E to increase their height to match that of the Style A. Since there is no data to suggest that Style A has been a problem for pilots to see, it made sense to make the lighting styles consistent.
B. Years ago, research was conducted that concluded pilots flying at heights above 800 feet AGL utilized the earth’s horizon for navigation, versus pilots below the 800 feet AGL tending to use the earths terrain for navigation and obstruction avoidance. Based on this research, lighting standards were established that called for red lights or paint to be used smaller obstructions, and for high intensity white lights to be used on taller obstructions. The higher intensity white lights were required to overpower the sunlight/glare that the pilot would be looking into once past the point of this horizon penetration (above 800 feet AGL), whereas the red lights and/or paint were enough to provide contrast against the terrain. It is important to note that at this time, medium intensity lights had not yet been introduced. As time went on, the medium intensity light was introduced and researchers tried to find a home for it in the older standards. As is evident with the later chronological designation as Style D and E (after the high intensity designations B and C), it was decided that the medium intensity would be placed on towers between 200 and 500 feet AGL. The 20,000cd lamp used with the medium intensity system has been proven to more than enough to provide the contrast necessary to mark obstructions at or below the 800 feet AGL where pilots will be looking below the horizon. At higher heights, the pilot will be looking towards the horizon and will need the higher light output of the high intensity lights to provide contrast against the sky . The new AC still has a 100 foot safety buffer between the referenced 800 foot cutoff by having the high intensity lights at 700 feet AGL.

C and D

C. It has been reported by the tower industry that some smaller FM stations are having financial difficulties in maintaining their towers to meet the FAA’s requirements for marking. Maintaining a towers red and white paint marking scheme is a very expensive maintenance item, and as a result, some facilities have not been able to repaint their towers to maintain compliance with the FAA’s rules. This has resulted in a small population of towers being out there that are not properly painted for daytime conspicuity. The only possible solution for these tower owners to consider would be to disregard their paint standards, refile with the FAA and propose the use of a high intensity white lighting configuration. Unfortunately, this can still cost over $100K for a 500 to 700 foot tall tower. In most cases, this is still too expensive for these tower owners to pay for. The new arrangement of tower heights that is provided in version AC 70/7460-1L CHG 1 of the AC now make medium intensity lighting styles available to these tower owners at a much lower cost that the high intensity. The FAA is hopeful that this more affordable option will allow tower owners to take action to bring their towers up to meeting the standard, thus improving aviation safety.
D. The category of towers that will be primarily affected by this change are those that are in the 500 to 700 foot AGL category, which is mostly small broadcasting towers. According to FAA obstruction data, this only accounts for approximately 2,000 towers in the US – out of the several hundred thousand towers that are already constructed. This is a very small percentage of towers that will be affected by the change

17. Could you please briefly describe the analysis your team conducted to address the medium dual lighting issues?

During an evaluation conducted in Michigan in 2013, researchers were able to conduct airborne evaluations of several towers in the area. The first notable finding was that pilots were unable to estimate the height of the towers unless they flew directly at the tower at a set altitude and could tell if the top of the tower fell on the horizon in front of them. From any sizable distance, the size of the tower really did not have any factor on the pilot. During the day, researchers agreed that the medium intensity lights were more than visible from several miles away. These flights reinforced the data suggested by the report reference above in which it was determined that pilots flying below 800 feet needed to see the contrasting light against the terrain, and that pilot operating above 800 feet looked off in the distance to the horizon and needed higher intensity lights to provide a higher contrast. At no time did any pilot indicate that the medium intensity lights were not providing enough conspicuity.

18. In attachments A-9, A-10, A-12 and A-13, the FAA indicates that when adding a 40’ pole and/or lightning rod, the structure height, not the overall height, is the determining factor for lighting configuration. So if an owner were to add a 40’ pole and a 20’ lightning rod to a 699’ AGL tower, would the owner still fall into the below 700’ rule? In the past, the total height of a structure was the driving factor for all notice and lighting determinations, is this a change to that rule?

If you have a 600’ tower, and add a 40’ pole and a 20’ lightning rod, and it is lit with red (figure A-6), the tower will fall in the next category (above 700’-1,050’) and will require 3-levels of lighting, white lighting is desired, medium intensity would not be applicable because it would be bumped above 700’. Therefore, it would require high intensity lighting. Under the high intensity rules, the appurtenance would be over 40’ (40’ pole plus 20’ lightning rod) requiring 3-levels of high intensity lighting and an additional fixture at the top of appurtenance (Figure A-9, configuration C3).

19. Historically the FAA required the total height filed to include any and all attachments and appurtenances to the tower, including lightning rods and light fixtures. The new attachments to the AC indicate that the required filing height is the structure only. Do the attachments to the AC change this filing requirement—i.e., to now file only the structure height?

The filing should reflect the total height of the obstruction including appurtenances. The diagrams that were added to the AC should be used to place the lighting on that structure. The appurtenance height (over or under 40 feet) plus the type of lighting desired will both come into play as to where the lights are placed. The filing process and the placement of lighting are two different processes.

20. Figure A-14 shows that L-810 side markers are no longer required on towers between 350’ – 700’. Does an owner need to file a new 7460-1 to remove the side markers (L-810s) for the existing towers between 350’ – 700’ or can the owner just remove the side markers?

Yes, owners of structures that received FAA determinations prior to December 4, 2015 need to file for a marking and lighting change in order to remove the side markers.

21. Are lighted marker balls automatically needed for transmission lines based on the line voltage? And If not automatically needed, how likely will an FAA review and determination require them in the project area based on the presence of nearby airports and canyon open space areas? If FAA can’t make a preliminary determination now, can additional parameters be provided around the circumstances where lighted marker ball would be mandated?

Yes, lighted catenary markers are required for lines 69kV and greater (AC 70/7460-1L CHG 1 para 3.5.1, 4.4.1, 10.2.1). An aeronautical study will be conducted to determine marking and lighting requirements for aviation safety. Notice to the FAA is required when the transmission line is 200 feet or more above the canyon floor/river.

22. Are the requirements for transmission lines only applicable to new construction and utility improvements?

These requirements have not changed but have been detailed in the new Marking and Lighting advisory due to the number of questions we have received from transmission line proponents.

23. Are the requirements for transmission lines applicable to new construction in existing utility ROW where comparable voltage transmission lines already exist with unlighted marker balls?

Yes, transmission lines greater than 69kV have always had the requirement for lighted marker balls.

24. Chapter 2, paragraph 2.2 discusses the marking of guy wires on 2000’ towers. Does this section only apply to towers 2000’ and greater in height? Please clarify the purpose of this paragraph.

This is relative to any guyed structure regardless of height. The 2000’ structure is an example case to demonstrate why properly maintained marking and lighting are important for increased conspicuity of guyed towers.

25. Paragraph 3.3.3 states that “to be effective, paint should be applied to all inner and outer surfaces of the framework.” But Paragraph 3.4.4(6) states that “coaxial cable, conduits, and other cables attached to the face of the tower” must be painted. Please clarify whether such cables, when installed within the skeletal framework of the tower, require painting.

If the “coaxial cable, conduits, and other cables” are not attached to the face of the tower, i.e., they are in the skeletal structure, they may be but would not have to be painted.

26. Paragraph 4.5 now states that light fixture lenses should be inspected every 24 months. Can the FAA explain how they arrived at this interval given that TIA only recommends climbed tower inspections (including lighting inspections) every 3 years for guyed towers and every 7 years for all other towers? Adding a climbed inspection every 2 years is unduly burdensome unless the FAA can justify the shortened interval.

TIA Inspection criteria is for their tower components, not for the marking and lighting. The FAA found three years for guyed towers and 7 years for other towers insufficient for tower lighting. This determination is based on post-repair reports on deterioration due to harsh environments. Effects noted include crazing, cracks, UV damage, dirt buildup, etc., that contributed to reduced light output. Therefore, the FAA recommends visual inspection every 24 months.

The intent of this requirement was not to inspect lights that have been “in place for only two years”. A two year period is adequate for performing an inspection of the light fixture lenses. As a fixture ages it will be more susceptible to deterioration and will be detected with this 24 month inspection requirement. There was no formal study looking at light fixture damage, but researchers witnessed several instances where fixtures were not being maintained as necessary. Tower owners have to ensure that the lighting continues to meet the FAA standards.
Visual inspection can be accomplished via ground inspection or via UAS as long as the person making the inspection can clearly see the fixture and be able to determine its condition. Climbed inspections may be preferred, but not required specifically for this purpose.

28. Does FAA have additional details on the lighting requirements for marker balls to include position and number of lights required?

Please review the Appendix A drawings, figures A1 thru A5.

29. On an existing 500ft Tower with alternating red and white bands using red incandescent lighting with flashing beacons located midway and top and steady slide lights 1/3 and 2/3 of the height: Do the steady side lights have to be maintained under the revision of the regulations?

If a client has an existing tower, with determination prior to Dec 4, that meets previous marking and lighting “K” criteria, they are not required to change marking and lighting. However, if they wish to change marking or lighting from what was specified in the initial determination, they should submit for a Marking and Lighting study on our website (https://oeaaa.faa.gov), requesting the change by submitting Form 7460-1. When filing, they should include the proposed change and note that it is consistent with AC 70/7460-1L CHG 1.

30. Paragraph 4.7(7) states that no object wider than 7/8 inch should be placed in front of any light. Please clarify the basis for the “7/8 inch rule.” Previously, when members inquired regarding the 7/8 inch rule, the FAA stated that it had no basis and a letter was issued stating that 1.25 inches was the appropriate maximum width, however, that with was similarly not supported. In the previous 1-K AC, any mention of a maximum object width was omitted, but it has now been reinserted.

The 7/8 rule was implemented because industry was not self-policing the amount of objects placed in front of lightbulbs. Also, with the introduction of LEDs this becomes more critical. LED light sources are much smaller when compared to traditional sources, so any object wider than 7/8-inch may block enough light to degrade perception in that direction.

31. The FAA stated in its response that the 7/8” rule was implemented because industry was not self-policing the amount of objects placed in front of light bulbs. Please provide a basis for this reasoning. Were studies conducted indicating industry was installing structures in front of light fixtures? Was a cost-benefit analysis performed? Considering the presence of lightning rods and other narrow diameter equipment that must be placed at the tops of towers, could you please provide clarification on whether the FAA is concerned about objects placed directly next to the light rather than objects placed one or more feet away from the light? Is there a distance from the light that an obstruction may be located?

There was no specific study done on this issue, nor was a cost benefit performed. The placement of an object 7/8” or thicker will block the light output of the fixture making the light invisible to pilots approaching the obstruction from behind the object. The larger the object; the larger area that is blocked. It is true that if the object is moved farther away from the light fixture, the area blocked will be reduced – but there is still an area that is blocked. Obstruction light fixtures are specially designed with a main beam and certain photometric characteristics that make them perform in a particular way. Placing an object larger than 7/8” thick in front of it has a direct impact on the photometrics. This is why the FAA limits the size of the object and/or requires a secondary light fixture to be installed to provide light into that blocked area.

32. Paragraph 4.10 states that “…in general light shields are not permitted…”, but paragraphs 6.7 and 7.5.2 state that shielding may be necessary. How will the FAA differentiate between the variations? Does shielding have to be requested, and if so, how will it be requested and approved? Who has approval authority on shielding and how do they determine if photometrics, bird nesting, or snow accumulation will be a factor?

Paragraph 6.7 is addressing very rare special cases in which lighting systems are causing a hazard to motorists, vessel operations, or pilots. This paragraph allows mitigation if existing lighting is identified as a hazard. The shielding must not derogate the lighting’s intended purposes. For an assessment on a case-by-case basis contact the FAA Office of Airports, Safety R&D Section. The baffling or shielding of lights is handled by the Airport Safety R&D Section based out of the FAA’s William J. Hughes Technical Center. In cases where baffling or shielding may be required, the OE group will coordinate with the Airport Safety R&D Section to coordinate the necessary research required to investigate the situation. Baffling and/or shielding of obstruction lighting is very rare and typically not permitted.

33. Paragraph 4.11 was newly added and requires coordination of lighting with the US Coast Guard for structures on waterways. Will the FAA coordinate with the Coast Guard before issuing the determination? What happens if the Coast Guard disagrees with the determination lighting? Could you please establish the point of contact at the Coast Guard, as well as provide a definition for the term “waterway”?

“Proximity to a navigable waterway” is undefined. Any light that may be a distraction to vessels should be first discussed with the Coast Guard. If the proponents believe this may be a factor, the FAA recommends contacting the Coast Guard as specified in Paragraph 4.11. Additionally, Industry is responsible for coordinating their structures with the Coast Guard and the FAA will collaborate with the Coast Guard to resolve any disagreements, should that happen.
Waterway is any navigable body of water. The contact information for the Coast Guard is listed in the AC within 4.11, but the phone number has been changed. The new number is 202-372-1546 and will be reflected in the next revision.
The mailing address is:
Commandant (CG-NAV-1),
U.S. Coast Guard,
2703 Martin Luther King Jr. Ave SE STOP 7418,
Washington, DC 20593-7418

34. Why does paragraph 2.4.3 Note 2, states that a NOTAM is automatically deleted from the system after 15 days even though the update to the E-NOTAM program that became effective last year allows for self-selection of the NOTAM period?

The 15-day note is an error. This is a carryover from the previous AC and should have been deleted. In an effort to streamline processes related to Notices to Airmen (NOTAMs), tower owners now have the option of self-selecting the amount of time their NOTAMs remain active. Tower owners still must notify the FAA within 30 minutes of discovery of any lighting outage or malfunction, and they must take steps to repair the faulty lighting as rapidly as possible. See 47 C.F.R. §17.48.
The revised publication is being coordinated within the FAA and will be posted soon.

35. How do I request the use of an Aircraft Detection Lighting System (ADLS)?

ADLS may be requested on initial filing of a new structure, as a separate marking and lighting study on a previously studied structure, or at the proponents request prior to issuance of a Determination. You must select an approved ADLS vendor with a Technical Note (TN) issued by the FAA. If you are unsure if the vendor has an approved TN you can search the Airports Division TN database by clicking the “Useful Links” on the left hand side of this page.

- Select “Aircraft Detection Lighting System (ADLS) Technical Notes”.
- In the Search window under the "Get Adobe Reader" graphic, begin typing “Aircraft Detection Lighting System”.
- A drop down will display a list of TNs. Select any of these to view the TN. (These are listed according to relevance to your “Search” and the date the TN was published/amended, NOT in any order of preference.)

The vendor will supply you with their “plan” based upon the requirements in the area (identifying any airports/heliports that may preclude approval of an ADLS). After receiving the radar coverage maps and any additional information that the vendor believes will be required due to the local area, file Notice through the oeaaa.faa.gov website.

a. If this is an existing project/structure include the prior Aeronautical Study Number (ASN).

b. The location of the sensor(s) must be filed separately (if not on the structure to be considered) with the frequencies/power included in the study. Do not include the sensor frequencies/power on any structure that does not have a sensor installed.

c. Upload all documentation including vendor’s name, radar coverage maps, any justification the vendor may have supplied to the use of their system in the area. Include in the uploaded documents a certifying statement from the owner of the structure(s) and the ADLS vendor. For example:

i. (company/name of manufacturer) certifies that the proposed installation of the ADLS for the project will meet the requirements of the current version of AC 70/7460-1 Obstruction Marking and Lighting, and will be in accordance with the most recent Technical Note issued for this system.

(signature of company official) (and date signed).

ii. (company/name of developer) certifies that the proposed ADLS for the project will be continuously monitored in accordance with the current version of AC 70/7460-1 Obstruction Marking and Lighting, and the Technical Note issued for the system. We will ensure this responsibility is specifically transferred to any subsequent owners of the project.

(signature of company official) (and date signed).

Become familiar with Chapter 14 of the current Advisory Circular 70/7460-1. There are data retention/monitoring requirements, etc. you will need to maintain to be in compliance.

The continued operation of the ADLS and compliance with the current Advisory Circular 70/7460-1 is YOUR responsibility. In the event of transfer of ownership, ensure the handoff of responsibility is completed.

If you have further questions regarding the filing of an ADLS study, contact the technician in your area. The technician contact information may be found via the “Off Airport Contacts” link on the left side of this page.